Is the world witnessing the demise of the U.S.-led liberal order? If so, this is not how it was supposed to happen. The great threats were supposed to come from hostile revisionist powers seeking to overturn the postwar order. The United States and Europe were supposed to stand shoulder to shoulder to protect the gains reaped from 70 years of cooperation. Instead, the world’s most powerful state has begun to sabotage the order it created. A hostile revisionist power has indeed arrived on the scene, but it sits in the Oval Office, the beating heart of the free world. Across ancient and modern eras, orders built by great powers have come and gone—but they have usually ended in murder, not suicide.

U.S. President Donald Trump’s every instinct runs counter to the ideas that have underpinned the postwar international system. Trade, alliances, international law, multilateralism, environmental protection, torture, and human rights—on all these core issues, Trump has made pronouncements that, if acted on, would bring to an end the United States’ role as guarantor of the liberal world order. He has broken with 70 years of tradition by signaling the end of U.S. support for the European Union: endorsing Brexit and making common cause with right-wing European parties that seek to unravel the postwar European project. In his inaugural address, Trump declared, “From this moment on, it’s going to be America first,” and he announced his intention to rethink the central accomplishments of the U.S.-led order—the trade and alliance systems. Where previous presidents have invoked the country’s past foreign policy triumphs, Trump describes “horrible deals” and allies that “aren’t paying their bills.” His is a vision of a dark and dangerous world in which the United States is besieged by Islamic terrorism, immigrants, and crime as its wealth and confidence fade. In his revisionist narrative, the era of Pax Americana—the period in which the United States wielded the most